Forming a through hole in a photoimageable dielectric structure

ABSTRACT

A through hole, and associated method of formation, through a layered structure that includes one or more layers having photoimageable dielectric (PID) material. The method forms a via within each such layer in isolation and then stacks the layers in a way that registers the vias over one another such that the through hole is formed as the sequentially registered vias. A sticker layer of the layered structure includes a cylindrical volume, an annular volume circumscribing the cylindrical volume, and a remaining volume surrounding the annular volume. The sticker layer preferentially includes a power plane of continuous metalization having a hole, wherein a perimeter of the hole surrounds the fully cured volume and circumscribes a portion of the remaining volume. During processing of the sticker layer, the sticker layer is photolithographically masked and exposed to ultraviolet radiation in a manner that leaves the cylindrical volume uncured, the annular volume fully cured, and the remaining volume partially cured. Then the PID material within the cylindrical volume is chemically developed away so as to leave a via in the sticker layer. During the stacking of the layers, the sticker layer is sandwiched between two dielectric layers. Subsequent pressurization of the stack causes the two dielectric layers to adhesively bond with the layer. During such pressurization, the fully cured annular volume prevents liquified and partially cured PID material in the remaining volume from flowing into the via of the layer.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to a method of forming a throughhole in a layered structure that includes a layer having aphotoimageable dielectric material.

[0003] 2. Related Art

[0004] An electrical structure, such as a printed circuit board,typically includes a stack of cores. A core is a dielectric layer withmetalization on either side. Such an electrical structure may includecores, such as 2 to 15 cores, laminated together with a layer ofdielectric material between each pair of cores. Following lamination, athough hole may be formed through the thickness of the overallstructure, such as by mechanical drilling or laser ablation, and thenplated with metal to facilitate electrical coupling between variouslayers of the structure. Alternatively, the through hole may be formedincrementally by forming a via in a layer after the layer has beenlaminated onto the stack, such that the via thus formed is properlyregistered over the corresponding via in the preceding layer of thestack. Thus, the through hole may formed in either in one step or in asequence of steps.

[0005] Drilling a through hole through a layered structure, such as bymechanical or laser drilling, is a very expensive step of the overallprocess and is often the most costly step. Moreover, it is not unusualfor some of such drilled holes to generate a defect in the structurethat necessitates discarding the structure, resulting in a yield losscoupled with loss of processing time. For example, the drilling maycause an unwanted pinhole or crack to form such that subsequent metallicplating of the structure results in plating of the pinhole which becomesa source of unwanted electrical shorting between conductive portions ofthe structure. Even greater costs may result from using the sequentialmethod because a yield loss will occur at each step in which a via isformed with the cumulative cost growing nonlinearly as more layers areadded.

[0006] A less costly method is needed to form a through hole in alayered dielectric structure.

SUMMARY OF THE INVENTION

[0007] The present invention provides a method for forming an electronicstructure, comprising the steps of:

[0008] providing a layer that includes: a cylindrical volume of aphotoimageable dielectric (PID) material, an annular volume of the PIDmaterial circumscribing the cylindrical volume, and a remaining volumeof the PID material circumscribing the annular volume;

[0009] photolithograhically exposing the layer to radiation;

[0010] fully curing the annular volume by said radiation;

[0011] partially curing the remaining volume by said radiation; and

[0012] preventing curing of the cylindrical volume, wherein the PIDmaterial in the cylindrical volume remains uncured.

[0013] The present invention provides a method for forming an electronicstructure having a through hole, comprising the steps of:

[0014] forming a layer that includes a via and an internal power planehaving a hole therethrough, wherein a fully cured volume of aphotoimageable dielectric (PID) material circumscribes the via, whereina partially cured remaining volume of the PID material circumscribes thefully cured volume, and wherein a perimeter of the hole in the powerplane surrounds the fully cured volume and circumscribes a portion ofthe remaining volume;

[0015] forming a first dielectric layer having a first via, wherein across-sectional area and shape of the first via is about the same as across-sectional area and shape of the via;

[0016] forming a second dielectric layer having a second via, wherein across-sectional area and shape of the second via is about the same asthe cross-sectional area and shape of the via;

[0017] forming a layered stack, wherein the layer is nonadhesivelysandwiched between the first dielectric layer and the second dielectriclayer, and wherein the via is registered between the first via and thesecond via; and

[0018] fully curing the remaining volume, wherein the PID material ofthe partially cured volume is prevented by the fully cured volume fromentering the via, wherein the layer becomes adhesively sandwichedbetween the first dielectric layer and the second dielectric layer, andwherein the electronic structure is formed such that the through holecomprises the first via, the via, and the second via.

[0019] The present invention provides a layer, comprising:

[0020] a cylindrical volume;

[0021] a fully cured annular volume of a photoimageable dielectric (PID)material circumscribing the cylindrical volume; and

[0022] a partially cured remaining volume of the PID materialcircumscribing the annular volume.

[0023] The present invention provides an electronic structure,comprising:

[0024] a layer that includes: a via, a fully cured volume of aphotoimageable dielectric (PID) material circumscribing the via, and apartially cured remaining volume of the PID material circumscribing thefully cured volume; and

[0025] a power plane between a first surface of the layer and a secondsurface of the layer, wherein the power plane includes a holetherethrough, wherein a perimeter of the hole in the power planesurrounds the fully cured volume and circumscribes a portion of theremaining volume.

[0026] The present invention provides a method forming an electronicstructure, comprising the steps of:

[0027] providing a layer that includes:

[0028] a cylindrical volume of a photoimageable dielectric (PID)material,

[0029] a first annular volume of the PID material circumscribing thecylindrical volume,

[0030] a second annular volume of the PID material circumscribing thefirst annular volume,

[0031] a remaining volume of the PID material circumscribing the secondannular volume, and

[0032] a power plane between a first surface of the layer and a secondsurface of the layer, wherein the power plane includes a holetherethrough, and wherein a perimeter of the hole in the power planecircumscribes the second annular volume;

[0033] photolithograhically exposing the layer to radiation;

[0034] partially curing the first annular volume by said radiation;

[0035] fully curing the second annular volume by said radiation;

[0036] partially curing the remaining volume by said radiation; and

[0037] preventing curing of the cylindrical volume.

[0038] The present invention provides an electronic structure,comprising:

[0039] a layer that includes: a via, a first partially cured volume of aphotoimageable dielectric (PID) material circumscribing the via, a fullycured volume of the PID material circumscribing the first partiallycured volume, and a second partially cured remaining volume of the PIDmaterial circumscribing the fully cured volume; and

[0040] a power plane between a first surface of the layer and a secondsurface of the layer, wherein the power plane includes a holetherethrough, wherein a perimeter of the hole in the power planecircumscribes the fully cured volume.

[0041] The present invention advantageously forms a through hole in alayered structure having a layer that includes PID material, by a methodwhich forms each layer and its via in isolation from the other layers,wherein a defect generated by formation of the via may result indiscarding the layer without discarding the layered structure.

[0042] The present invention has the advantage of providing a fullycured annulus around a via within a layer of PID material, so thatpartially cured PID material cannot move into the via when the layeredstructure that includes the layer is subject to pressurization and/orelevated temperature.

[0043] The present invention has the advantage of forming photovias,which is a less expensive process than that of forming laser-drilledvias.

[0044] The preceding advantages facilitate lower fabrication costs,reduced cycle time, and improved quality assurance. Thus, the presentinvention has the overall advantage of providing an inexpensive methodof forming a through hole in a layered dielectric structure having PIDmaterial in at least one layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045]FIG. 1 depicts a front cross-sectional view of a layer thatincludes photoimageable dielectric (PID) material, in accordance withpreferred embodiments of the present invention.

[0046]FIG. 2 depicts FIG. 1 with the layer divided into distinctvolumes, including a cylindrical volume.

[0047]FIG. 2A depicts the axial structure of the cylindrical volume ofFIG. 2.

[0048]FIG. 3 depicts the layer of FIG. 2 showing a firstphotolithographic masking and exposure, in accordance with a firstpreferred embodiment of the present invention.

[0049]FIG. 4 depicts the layer of FIG. 2 showing a secondphotolithographic masking and exposure, in accordance with the firstpreferred embodiment of the present invention.

[0050]FIG. 5 depicts the layer of FIG. 2 showing a photolithographicmasking and exposure, in accordance with a second preferred embodimentof the present invention.

[0051]FIG. 6 depicts the layer of FIG. 2 after the photolithographicmasking and exposure shown in FIGS. 3 and 4, or in FIG. 5.

[0052]FIG. 7 depicts FIG. 2 with a modification of the volume structureand showing a photolithographic masking and exposure, in accordance witha third preferred embodiment of the present invention.

[0053]FIG. 8 depicts the layer of FIG. 7 after the photolithographicmasking and exposure shown in FIG. 7.

[0054]FIG. 9 depicts FIG. 2 with a modification of the volume structureand showing a photolithographic masking and exposure, in accordance witha fourth preferred embodiment of the present invention.

[0055]FIG. 10 depicts the layer of FIG. 9 after the photolithographicmasking and exposure shown in FIG. 9.

[0056]FIG. 11 depicts FIG. 6 after the photolithographically masked andexposed layer of FIG. 6 is sandwiched between two 2S/1P layers to form alayered stack.

[0057]FIG. 12 depicts FIG. 11 after additional layers having PIDmaterial are added to opposite sides of the layered stack.

DETAILED DESCRIPTION OF THE INVENTION

[0058]FIG. 1 illustrates a front cross-sectional view of a layer 10 thatincludes photoimageable dielectric (PID) material 20, in accordance withpreferred embodiments the present invention. Any PID material known toone skilled in the art may be used in the resent invention, such asimproved photoimagable cationically polymerizable epoxy based coatingmaterials whose compositions are described in U.S. Pat. No. 5,026,624(Day et al., Jun. 25, 1991) and U.S. Pat. No. 5,300,402 (Card, Jr. etal., Apr. 5, 1994). The PID material 20, if uncured, flows when subjectto pressurization and/or elevated temperature. The propensity of the PIDmaterial 20 to flow diminishes as it undergoes a curing process. Forthis invention, a given specimen of PID material may exist in one of thefollowing states of cure: uncured, partially cured, and fully cured. Aspecimen of PID material is “uncured” if the specimen has experienced nocuring or negligible curing. A specimen of PID material is “partiallycured” if the specimen has been cured to an extent that it will flow ordeform, so as to nonadhesively couple with a contacting dielectric layerwhen subject to atmospheric pressure at ambient temperature, andadhesively bond with the contacting dielectric layer under subsequentpressurization and/or elevated temperature. A dielectric material thathas been partially cured in the preceding manner is known to one skilledin the art as B-staged material. A specimen of PID material is “fullycured” if the specimen has been cured to such an extent that the PIDmaterial will not substantially flow, or substantially deform, ifsubject to subsequent pressurization and/or elevated temperature. Themagnitude of pressurization and/or elevated temperature needed toeffectuate adhesive bonding depends on, inter alia, such factors as: thedegree of partial curing achieved prior to the pressurization and/orelevated temperature, the particular PID material that has beenpartially cured, and the roughness of the surface to which the partiallycured PID material will be subsequently bonded. The elevatedtemperature(s) may be achieved in various ways such as with multipleheating cycles. Pressures in a range of about 100 psi to about 700 psi,coupled with elevated temperatures in a range of about 80° C. to about250° C., have been found to be effective for full curing the B-stagedmaterials.

[0059] For the present invention, partial curing is accomplished bylimited exposure of the PID material to radiation, such as ultravioletradiation, and may be improved by accompanying and/or following theradiation exposure with heating such as at a temperature in a range ofabout 100° C. to about 150° C. for a period of time between about 3minutes and about 15 minutes. Also for the present invention, fullcuring is accomplished either by exposure to radiation such asultraviolet radiation of sufficient intensity and time to effectuatefull curing, or by subjecting partially cured PID material to acombination of pressurization and temperature elevation. Partial curingand full curing by exposure of the PID material to radiation isdifferentiated by the amount of radiant energy absorbed by the PIDmaterial, which is determined by such variables as the energy flux F (insuch units as milliwatts/cm²) of the radiation passing through the PIDmaterial and the total time T of exposure to the radiation, or moreparticularly on the dose FT. The range of FT that distinguishes partialcuring from full curing depends on the specific PID material usedinasmuch as each different PID material has its own characteristicchemical response to the incident radiation. One skilled in the art maydetermine practical ranges of FT for effectuating either full curing orpartial curing, without undue experimentation, by varying FT throughcontrol of F and T for individually cured PID samples, followed bytesting to determine whether the cured PID samples undergo liquificationand flow upon subsequent pressurization and exposure to elevatedtemperatures.

[0060] The layer 10 preferably includes a power plane 30 having a hole32 therethrough. A power plane is a layer of metal, such as copper,having one or more holes. The hole 32 is bounded by its perimeter, whichis the cylindrical surface 34 of the power plane 30. The hole 32 isfilled with the PID material 20. Thus, the PID material 20 iscontinuously distributed from the upper portion 12 to the lower portion13 of the layer 10. While FIG. 1 shows the power plane 30 asapproximately equidistant from a surface 15 and a surface 16 of thelayer 10, the power plane 30 may be located at any distance from thesurface 15 and the surface 16. The power plane 30 is required for someembodiments and is optional for other embodiments. Unless otherwisestated, the power plane 30 is assumed to be present.

[0061] An important characteristic of PID material is that negativelyacting PID material, if not exposed to the radiation that it issensitive to such as ultraviolet radiation, may be chemically developedaway by any method known to one of ordinary skill in the art. Note thatif the PID material is positively acting, the PID material actuallyexposed to the radiation would be developed away, which wouldnecessitate an-inversion of the masking schemes described herein inwhich portions of a given mask shown and described herein as opaquewould be instead transparent and portions of the given mask shown anddescribed herein as transparent would be instead opaque. The specificmethod and the chemicals that may be used for developing away the PIDmaterial, including wet chemicals and dry chemicals, depends on thechemical composition of the PID material. In contrast, radiationexposure of PID material causes chemical cross-linking reactions in thePID material, which renders the PID material resistant to beingchemically washed away by a developer solution. Thus, photovias may beformed in the layer 10 by photolithographic masking schemes that preventthe radiation from reaching those volumes of the layer 10 in whichphotovias are to be formed, but which allow radiation to interact withthe other volumetric portions of the layer 10 which may be subsequentlyexposed to the developer solution. The present invention includes, interalia, four such photolithographic embodiments, which are described infraherein.

[0062]FIG. 2 illustrates FIG. 1, wherein the space of the PID material20 is divided into distinct volumes: a cylindrical volume 70, an annularvolume 60 circumscribing the cylindrical volume 70, and a remainingvolume 50 circumscribing the annular volume 60. Definitionally,circumscribing includes surrounding and contacting. Also definitionally,a cylindrical volume is a three-dimensional volumetric shape having anaxis therethrough such that a cross section of the cylindrical volumehas a shape and area that are each invariant to position along the axis.FIG. 2A illustrates the axial structure of the cylindrical volume 70,wherein the cross section 77 of the cylindrical volume 70 is invariantto a position P of the cross section 77 in the direction 75 along theaxis 78 of the cylindrical volume 70. The direction 75 also appears inFIG. 2 to clarify the orientation of the cylindrical volume 70 in FIG.2A relative to the layer 10 in FIG. 2. While the shape of the crosssection, such as the cross section 77 of FIG. 2A, of a cylindricalvolume may be that of a circle, the shape may also be that of, interalia, an ellipse or a square.

[0063] Returning to FIG. 2, the remaining volume 50 includes the portion51, which is a volume between the power plane 30 and the annular volume60. As the portion 51 of the remaining volume 50 diminishes in size andapproaches a null (i.e., zero) volume, the portion 51 disappears suchthat the power plane 30 approaches circumscribing the annular volume 60.This limiting case is an optional form of the first and secondembodiments of the present invention, whereas this limiting case isrequired for the third and fourth embodiments of the present invention.

[0064] The first preferred embodiment of the present invention utilizestwo masking schemes in succession. FIG. 3 illustrates FIG. 2 showing afirst photolithographic masking and exposure, in accordance with thefirst preferred embodiment of the present invention. In FIG. 3, aradiation source 120 directs radiation 130, such as ultravioletradiation, of energy flux F₁ for a time duration T₁ through a mask 100located over the surface 15 of the layer 10 and then through the layer10. In relation to the radiation 130, the mask 100 includes an opaqueportion 102 over the cylindrical volume 70, a transparent portion 104over the annular volume 60, and an opaque portion 106 over the remainingvolume 50. Definitionally, a material is opaque or transparent if opaqueor transparent, respectively, to an incident radiation. Thus, the opaqueportion 102 and the transparent portion 104 are respectively opaque andtransparent to the radiation 130. The radiation source 140 directsradiation 150, such as ultraviolet radiation, of energy flux F₂ for atime duration T₂ through a mask 110 located over the surface 16 of thelayer 10 and then through the layer 10. In relation to the radiation150, the mask 110 includes an opaque portion 112 over the cylindricalvolume 70, a transparent portion 114 over the annular volume 60, and anopaque portion 116 over the remaining volume 50. F₁ T₁ and F₂ T₂ arepreferentially about equal and should not differ by more than about 10%.The radiation source 120 may be operated before, after, or concurrentwith the radiation source 140. Alternatively, either the radiationsource 120 or the radiation source 140 may be omitted since the annularvolume 60 can be accessed by either the radiation 130 or the radiation150, regardless of whether the power plane 30 is present or absent. Theenergy absorbed by the annular volume 60 from the radiation 130 and/orthe radiation 150 should be high enough to fully cure the annular volume60, or high enough to initiate a full cure of the annular volume 60followed by heating to effectuate the full cure of the annular volume 60if the radiation is accompanied with, or followed by, heating. Thisnecessitates that F₁T₁+F₂T₂ be of a sufficiently high magnitude that canbe determined without undue experimentation, as explained supra.

[0065]FIG. 4 illustrates FIG. 2 showing a second photolithographicmasking and exposure, in accordance with the first preferred embodiment.In FIG. 4, the radiation source 120 directs radiation 130, such asultraviolet radiation, of energy flux F₃ for a time duration T₃ througha mask 200 located over the surface 15 of the layer 10 and then throughthe layer 10. In relation to the radiation 130, the mask 100 includes anopaque portion 202 over the cylindrical volume 70, and a transparentportion 204 over the annular volume 60 and over the remaining volume 50.

[0066] With the power plane 30 present, the radiation 130 cannot accessa portion of the remaining volume 50 situated between the power plane 30and the surface 16 of the layer 10, so that the radiation source 140must be used. The radiation source 140 directs radiation 150 of energyflux F₄ for a time duration T₄, such as ultraviolet radiation, through amask 210 located over the surface 16 of the layer 10 and then throughthe layer 10. In relation to the radiation 150, the mask 210 includes anopaque portion 212 over the cylindrical volume 70, and a transparentportion 214 over the annular volume 60 and over the remaining volume 50.F₃ T₃ and F₄ T₄ are preferentially about equal and should not differ bymore than about 10%. The radiation source 120 may be operated before,after, or concurrent with the radiation source 140. If the power plane30 is absent, the radiation source 140 and associated radiation 150 arenot required and may be omitted. The energy absorbed by the remainingvolume 50 from the radiation 130 and/or the radiation 150 should bebounded so to partially cure, but not fully cure, the remaining volume50. This necessitates that F₃T₃ and F₄T₄ be of a sufficiently lowmagnitude that can be determined without undue experimentation, asexplained supra.

[0067] For the first preferred embodiment, the first photolithographicmasking and exposure (see FIG. 3) may be executed either before or afterthe second photolithographic masking and exposure (see FIG. 4). FIG. 6shows an appearance of the layer 10 after execution of the firstphotolithographic masking and exposure and the second photolithographicmasking and exposure. In FIG. 6, the cylindrical volume 70 isrepresented as an uncured volume 72, the annular volume 60 has become afully cured volume 62, and the remaining volume 50 has become apartially cured volume 52. The uncured volume 72 is a consequence of theopaque portion 102, 112, 202, and 212 of the masks 100, 110, 200, and210, respectively. The uncured volume 72 may be chemically developedaway to form a via. For example, FIG. 11 shows the via 73 which resultsfrom a developing away of the PID material in the uncured volume 72 ofFIG. 6.

[0068]FIG. 5 illustrates the layer of FIG. 2 showing a photolithographicmasking and exposure, in accordance with the second preferred embodimentof the present invention. In FIG. 5, the radiation source 120 directsradiation 130, such as ultraviolet radiation, of energy flux F₅ for atime duration T₅ through a mask 300 located over the surface 15 of thelayer 10 and then through the layer 10. In relation to the radiation130, the mask 300 includes a portion 302 having an optical density D₁over the cylindrical volume 70, a portion 304 having an optical densityD₂ over the annular volume 60, and a portion 306 having an opticaldensity D₃ over the remaining volume 50, wherein D₁>D₃>D₂. Opticaldensity, which is defined as 31 log₁₀ of the transmissivity, relates toa fraction of incident radiation 130 transmitted through the mask 300;i.e., the fraction of radiation 130 transmitted through a given portionof the mask 300 decreases as the optical density of the given portionincreases. A purely transparent material has an optical density of zero,while a purely opaque material has an optical density of infinity.

[0069] With the power plane 30 present, the radiation 130 cannot accessa portion of the remaining volume 50 situated between the power plane 30and the surface 16 of the layer 10, so that the radiation source 140must be used. The radiation source 140 directs radiation 150 of energyflux F₆ for a time duration T₆, such as ultraviolet radiation, through amask 310 located over the surface 16 of the layer 10 and then throughthe layer 10. In relation to the radiation 150, the mask 310 includes aportion 312 having an optical density D₄ over the cylindrical volume 70,a portion 314 having an optical density D₅ over the annular volume 60,and a portion 316 having an optical density D₆ over the remaining volume50, wherein D₄>D₆>D₅. F₅T₅ and F₆T₆ are preferentially about equal andshould not differ by more than about 10%. If the power plane 30 isabsent, the radiation source 140 and associated radiation 150 areunnecessary and may be omitted.

[0070] For given values of F₃T₃ and F₄T₄ associated with the radiation130 and the radiation 150, respectively, the optical densities D₁ and D₄should be sufficiently high that the cylindrical volume 70 remainsuncured, the optical densities D₂ and D₅ should be sufficiently low thatthe annular volume 60 becomes fully cured (or low enough to initiate afull cure of the annular volume 60 followed by heating to effectuate thefull cure of the annular volume 60 if the radiation is accompanied with,or followed by, heating), and the optical densities D₃ and D₆ should bein a range that ensures partial curing and prevents full curing. Forgiven values of F₃T₃ and F₄T₄, one skilled in the art may determinepractical values of D₁, D₂, D₃, D₄, D₅ and D₆ without undueexperimentation by parametrically varying D₁, D₂, D₃, D₄, D₅, and D₆until the aforementioned curing configuration of the layer 10 isachieved. Alternatively, one skilled in the art may use his or herexperience to estimate practical values of D₁, D₂, D₃, D₄, D₅, and D₆,and then, without undue experimentation, parametrically vary F₃T₃ andF₄T₄ until the aforementioned curing configuration of the layer 10 isachieved. In accordance with the preceding methodology, D₁, D₂, D₃, D₄,D₅, and D₆ may be adjusted such that the portion 302 of the mask 300 isopaque over the cylindrical volume 70, the portion 304 of the mask 300is transparent over the annular volume 60, the portion 306 of the mask300 is partially transparent over the remaining volume 50, the portion312 of the mask 310 is opaque over the cylindrical volume 70, theportion 314 of the mask 310 is transparent over the annular volume 60,and the portion 316 of the mask 310 is partially transparent over theremaining volume 50. A portion of a mask is partially transparent if theportion of the mask transmits a portion of the total incident radiativeflux that partially cures a portion of the layer 10 that is exposed tothe portion of the radiative flux.

[0071]FIG. 6, which was discussed infra in connection with the firstembodiment, also shows the appearance of the layer 10 after execution ofthe photolithographic masking and exposure for the second embodiment. Aswith the first embodiment, the cylindrical volume 70 is represented asan uncured volume 72, the annular volume 60 has become a fully curedvolume 62, and the remaining volume 50 has become a partially curedvolume 52. The uncured volume 72 may be chemically developed away toform a via. For example, FIG. 11 shows the via 73 which results fromdeveloping away the PID material in the uncured volume 72 of FIG. 6.

[0072]FIG. 7 illustrates FIG. 2 with a modification of the volumestructure and showing a photolithographic masking and exposure, inaccordance with a third preferred embodiment of the present invention.In FIG. 7, the portion 51 of the remaining volume 50 of FIG. 2 has beeneliminated such that the remaining volume 50 has been replaced by theremaining volume 55, and an annular volume 60 has been replaced by theannular volume 65 such that the power plane 30 circumscribes the annularvolume 65 at the cylindrical surface 34 of the power plane 30. In FIG.7, the radiation source 120 directs radiation 130 of energy flux F₇ fora time duration T₇, such as ultraviolet radiation, through a mask 400located over the surface 15 of the layer 10 and then through the layer10. In relation to the radiation 130, the mask 400 includes an opaqueportion 402 over the cylindrical volume 70, and a transparent portion404 over the annular volume 65 and over the remaining volume 55.

[0073] Due to the presence of the power plane 30, the radiation 130cannot access a portion of the remaining volume 55 situated between thepower plane 30 and the surface 16 of the layer 10, so that the radiationsource 140 must be used. The radiation source 140 directs radiation 150,such as ultraviolet radiation, of energy flux F₈ for a time duration T₈through a mask 410 located over the surface 16 of the layer 10 and thenthrough the layer 10. In relation to the radiation 150, the mask 410includes an opaque portion 412 over the cylindrical volume 70, and atransparent portion 414 over the annular volume 65 and over theremaining volume 55. F₇ T₇ and F₈ T₈ are preferentially about equal andshould not differ by more than about 10%. The radiation source 120 maybe operated before, after, or concurrent with the radiation source 140.Note that the power plane 30 must be present in the third embodiment.The energy absorbed by the remaining volume 55 from the radiation 130and the radiation 150 should be bounded so as to partially cure, but notfully cure, the remaining volume 55. This necessitates that F₇T₇ andF₈T₈ be of a sufficiently low magnitude. On the other hand, F₇T₇+F₈T₈must be high enough to fully cure the annular volume 65, or high enoughto initiate a full cure of the annular volume 65 followed by heating toeffectuate the full cure of the annular volume 65 if the radiation isaccompanied with, or followed by, heating. For the case in which F₇T₇ isequal to about F₈T₈, the time-integrated radiant energy flux absorbed bythe annular volume 65 (i.e., 2F₇T₇) is about twice the time-integratedradiant energy flux absorbed by the remaining volume 55 (i.e., F₇T₇).Practical values of F₇T₇ and F₈T₈ that satisfy the preceding curingrequirements can be determined without undue experimentation byparametric studies involving F₇, T₇, F₆, and T₈, as explained supra.

[0074]FIG. 8 shows the appearance of the layer 10 after execution of thephotolithographic masking and exposure for the third embodiment. Thecylindrical volume 70 is represented as an uncured volume 71, theannular volume 65 has become a fully cured volume 66, and the remainingvolume 55 has become a partially cured volume 56. The uncured volume 71is a consequence of the opaque portions 402 and 412 of the masks 400 and410, respectively. The uncured volume 71 in FIG. 8 may be chemicallydeveloped away to form a via in the same manner as the uncured volume 72in FIG. 6 may be chemically developed away to form a via as wasexplained supra.

[0075]FIG. 9 illustrates FIG. 2 with a modification of the volumestructure and showing a photolithographic masking and exposure, inaccordance with a fourth preferred embodiment of the present invention.In FIG. 9, the portion 51 of the remaining volume 50 of FIG. 2 has beeneliminated such that the remaining volume 50 has been replaced by theremaining volume 58, and an annular volume 68 has replaced the annularvolume 60 of FIG. 2 such that the power plane 30 circumscribes theannular volume 68 at the cylindrical surface 34 of the power plane 30.Additionally, the cylindrical volume 70 of FIG. 2 has been replaced by acylindrical volume 85 and an annular volume 80 circumscribing thecylindrical volume 85, such that the annular volume 68 circumscribes theannular volume 80. In FIG. 9, the radiation source 120 directs radiation130 of energy flux Fg for a time duration T₉, such as ultravioletradiation, through a mask 450 located over the surface 15 of the layer10 and then through the layer 10. In relation to the radiation 130, themask 450 includes an opaque portion 452 over the cylindrical volume 85,and a transparent portion 454 over the annular volume 80, over theannular volume 68, and over the remaining volume 58.

[0076] Due to the presence of the power plane 30, the radiation 130cannot access a portion of the remaining volume 58 situated between thepower plane 30 and the surface 16 of the layer 10, so that the radiationsource 140 must be used. The radiation source 140 directs radiation 150of energy flux F₁₀ for a time duration T₁₀, such as ultravioletradiation, through a mask 460 located over the surface 16 of the layer10 and then through the layer 10. In relation to the radiation 150, themask 460 includes an opaque portion 462 over the cylindrical volume 85and over the annular volume 80, and a transparent portion 464 over theannular volume 68 and over the remaining volume 58. F₉T₉ and F₁₀T₁₀ arepreferentially about equal and should not differ by more than about 10%.The radiation source 120 may be operated before, after, or concurrentwith the radiation source 140. Note that the power plane 30 must bepresent in the fourth embodiment. The energy absorbed by the remainingvolume 58 from the radiation 130 and the radiation 150 should be boundedso to partially cure, but not fully cure, the remaining volume 58. Thisnecessitates that F₉T₉ and F₁₀T₁₀ be of a sufficiently low magnitude. Onthe other hand, F₉T₉+F₁₀T₁₀, must be high enough to fully cure theannular volume 68, or high enough to initiate a full cure of the annularvolume 68 followed by heating to effectuate the full cure of the annularvolume 68 if the radiation is accompanied with, or followed by, heating.Moreover, since the opaque portion 462 prevents the radiation 150 fromreaching the annular volume 80, the annular volume 80 will be partiallycured if the remaining volume 58 is partially cured. For the case inwhich F₉T₉ is equal to about F₁₀T₁₀, the time-integrated radiant energyflux absorbed by the annular volume 68 (i.e., 2F₉T₉) is about twice thetime-integrated radiant energy flux absorbed by the remaining volume 58as well as by the annular volume 80 (i.e., F₉T₉). Practical values ofF₉T₉ and F₁₀T₁₀ that satisfy the preceding curing requirements can bedetermined without undue experimentation by parametric studies involvingF₉, T₉, F₁₀, and T₁₀ as explained supra.

[0077]FIG. 10 shows the appearance of the layer 10 after execution ofthe photolithographic masking and exposure for the fourth embodiment.The cylindrical volume 85 is represented as an uncured volume 87, theannular volume 80 has become a partially cured volume 82, the annularvolume 68 has become a fully cured volume 69, and the remaining volume58 has become a partially cured volume 59. The uncured volume 87 is aconsequence of the overlapping portions of the opaque portions 452 and462 of the masks 450 and 460, respectively. The uncured volume 87 inFIG. 10 may be chemically developed away to form a via in the samemanner as the uncured volume 72 in FIG. 6 may be chemically developedaway to form a via as was explained supra.

[0078] Note that a via thus formed in place of the uncured volume 87 isadjacent to the partially cured volume 82. Thus, during subsequentpressurization and/or elevated temperature, partially cured PID materialmay flow from the partially cured volume 82 into the via thus formedfrom the uncured volume 87. This is potentially advantageous in caseswhere a small crevice or space may develop between layers of a layeredstack, such as the layered stack 999 described infra in conjunction withFIGS. 11 and 12, that includes the layer 10 of FIG. 10. The partiallycured PID material that flows from the partially cured volume 82 intothe via formed from the uncured volume 87 may advantageously fill theunwanted crevice or space between layers, which insulatively protectsagainst electrical shorting that may occur between subsequent plating ofthe via and nearby conductive material located within the layered stack.Noting that the PID material within the via may cause subsequentmetallic plating thickness variability, it is desirable to control thevolume of the uncured volume 87 to be small enough to reduce any suchplating thickness variability to levels that can be tolerated. Notingthat the volume of the uncured volume 87 is proportional to thedifferential in cross-section area of the opaque portion 452 of the mask450 and the opaque portion 462 of the mask 460, the volume of theuncured volume 87 may be controlled by adjusting the cross-section areaof the portions 452 and 462. The cross-section area of the portion 452is the area of the portion 452 that is exposed to the radiation 130. Thecross-section area of the portion 462 is the area of the portion 462that is exposed to the radiation 150.

[0079]FIG. 11 depicts FIG. 6 after the photolithographically masked andexposed layer 10 is sandwiched between a 2S/1P layer 500 and a 2S/1Player 600, to form a layered stack 999, wherein the uncured volume 72 ofFIG. 6 has been chemically developed away and is replaced by a via 73 asshown in FIG. 11. A 2S/1P layer generally comprises a dielectric layerwith an internal power layer, a signal layer on a bounding surface ofthe dielectric layer, and another signal layer on another boundingsurface of the dielectric layer. A signal plane is a layer of conductivecircuit lines. The 2S/1P layer 500 and the 2S/1P layer 600 may eachcomprise any dielectric material such as, inter alia, a PID material ora filled dielectric material containing a filler such as, inter alia,silica, alumina, dolomite, mica, and talc. The 2S/1P layer 500 includesa dielectric layer 510, a power plane 520, a signal plane 540, and asignal plane 550. Additionally, the 2S/1P layer 500 includes a via 530that is registered over the via 73, wherein the via 530 includes a crosssection of about the same size and shape as a cross section of the via73. As shown, the dielectric layer 510 includes a fully cured material,wherein the dielectric layer 510 could include a drilled hole with orwithout metal plating. Alternatively, the dielectric layer 510 couldinclude a fully cured ring of dielectric material (analogous to thefully cured volume 62) surrounding the via 530 and a partially curedvolume of dielectric material (analogous to the partially cured volume52) circumscribing the fully cured ring. The 2S/1P layer 600 includes adielectric layer 610, a power plane 620, a signal plane 640, and asignal plane 650. Additionally, the 2S/1P layer 600 includes a via 630that is registered over the via 73, wherein the via 630 includes a crosssection of about the same size and shape as a cross section of the via73. As shown, the dielectric layer 610 includes a fully cured material,wherein the dielectric layer 610 could include a drilled hole with orwithout metal plating. Alternatively, the dielectric layer 610 couldinclude a fully cured ring of dielectric material (analogous to thefully cured volume 62) surrounding the via 630 and a partially curedvolume of dielectric material (analogous to the partially cured volume52) circumscribing the fully cured ring. FIG. 11 shows a through hole940 that includes the sequential arrangement of the via 530, the via 73,and the via 630. The partially cured volume 52 of the layer 10 willbecome fully cured upon subsequent pressurization and/or elevatedtemperature, which will cause both the 2S/1P layer 500 and the 2S/1Player 600 to become adhesively bonded to the layer 10. During thesubsequent final lamination step of pressurization and/or elevatedtemperature, the fully cured volume 62 will prevent liquified PIDmaterial from the partially cured volume 52 from flowing into the via73, the fully cured ring (if it exists) of dielectric material in thedielectric layer 510 will prevent liquified PID material from thecircumscribing partially cured volume of dielectric material in thedielectric layer 610 from flowing into the via 530, and the fully curedring (if it exists) of dielectric material in the dielectric layer 610it will prevent liquified PID material from the circumscribing partiallycured volume of dielectric material in the dielectric layer 610 fromflowing into the via 630. The layer 10 is called a “sticker layer,”because the layer 10 serves to interfacially bond the 2S/1P layer 500and the 2S/1P layer 600 together in conjunction with the finallamination step of pressurization and/or elevated temperature.

[0080]FIG. 12 depicts FIG. 11 after additional layers 700 and 800 areadded to opposite sides of the layered stack 999 prior to the finallamination step of pressurization and/or elevated temperature. The layer700 is stacked on the 2S/1P layer 500 and includes a partially curedvolume 710 of PID material, a via 730 that is registered over the via530 wherein the via 730 includes a cross section of about the same sizeand shape as a cross section of the via 73, and a fully cured volume 720of PID material that circumscribes the via 730. The layer 800 is stackedon the 2S/1P layer 600 and includes a partially cured volume 810 of PIDmaterial, a via 830 that is registered over the via 630 wherein the via830 includes a cross section of about the same size and shape as a crosssection of the via 73, and a fully cured volume 820 of PID material thatcircumscribes the via 830. FIG. 12 shows the through hole 940 as anelongated variant of the through hole 940 in FIG. 11 such that thethrough hole 940 of FIG. 12 includes the sequential arrangement of thevia 730, the via 530, the via 73, the via 630, and the via 830. Thepartially cured volumes 710, 810, and 52, along with any partially curedvolumes that may exist in the 2S/1P layers 500 and 600, will becomefully cured upon a subsequent final lamination step of pressurizationand/or elevated temperature. The final lamination step which will causethe layers 700 and 800 to respectively bond adhesively with the 2S/1Players 500 and 600, in addition to causing the 2S/1P layers 500 and 600to each bond adhesively with the layer 10. During the subsequent finallamination step of pressurization and/or elevated temperature, the fullycured volume 720 will prevent liquified PID material from the partiallycured volume 710 from flowing into the via 730, the fully cured volume820 will prevent liquified PID material from the partially cured volume810 from flowing into the via 830, the fully cured volume 62 willprevent liquified PID material from the partially cured volume 52 fromflowing into the via 73, the fully cured ring (if it exists) ofdielectric material in the dielectric layer 510 will prevent liquifiedPID material from the circumscribing partially cured volume ofdielectric material in the dielectric layer 610 from flowing into thevia 530, and the fully cured ring (if it exists) of dielectric materialin the dielectric layer 610 it will prevent liquified PID material fromthe circumscribing partially cured volume of dielectric material in thedielectric layer 610 from flowing into the via 630. While FIG. 12depicts a five-layer structure, the invention embodied by FIG. 12 couldinclude any number of layer, such as 17 or more layers, wherein alllayers each include a partially cured ring of dielectric material oralternating layers each include a partially cured ring of dielectricmaterial.

[0081] While preferred and particular embodiments of the presentinvention have been described herein for purposes of illustration, manymodifications and changes will become apparent to those skilled in theart. Accordingly, the appended claims are intended to encompass all suchmodifications and changes as fall within the true spirit and scope ofthis invention.

We claim:
 1. A method for forming an electronic structure, comprisingthe steps of: providing a layer that includes: a cylindrical volume of aphotoimageable dielectric (PID) material, an annular volume of the PIDmaterial circumscribing the cylindrical volume, and a remaining volumeof the PID material circumscribing the annular volume;photolithograhically exposing the layer to radiation; fully curing theannular volume by said radiation; partially curing the remaining volumeby said radiation; and preventing curing of the cylindrical volume,wherein the PID material in the cylindrical volume remains uncured. 2.The method of claim 1, wherein the photolithograhically exposing stepincludes: forming a first mask over a first surface of the layer,wherein the first mask is opaque over the cylindrical volume,transparent over the annular volume, and opaque over the remainingvolume; passing said radiation through the first mask, onto the firstsurface, and through the layer; removing the first mask; forming asecond mask over the first surface of the layer, wherein the second maskis opaque over the cylindrical volume, transparent over the annularvolume, and transparent over the remaining volume; passing saidradiation through the second mask, onto the first surface, and throughthe layer; and removing the second mask.
 3. The method of claim 2,wherein the layer in the providing step includes a power plane betweenthe first surface of the layer and a second surface of the layer,wherein the power plane includes a hole therethrough, wherein aperimeter of the hole in the power plane surrounds the annular volumeand circumscribes a portion of the remaining volume, and wherein thephotolithograhically exposing step further includes: forming a thirdmask over the second surface of the layer, wherein the third mask isopaque over the cylindrical volume, transparent over the annular volume,and opaque over the remaining volume; passing said radiation through thethird mask, onto the second surface, and through the layer; removing thethird mask; forming a fourth mask over the second surface of the layer,wherein the fourth mask is opaque over the cylindrical volume,transparent over the annular volume, and transparent over the remainingvolume; passing said radiation through the fourth mask, onto the secondsurface, and through the layer; and removing the fourth mask.
 4. Themethod of claim 1, wherein the photolithograhically exposing stepincludes forming a first mask over a first surface of the layer andsubsequently passing said radiation through the first mask, onto thefirst surface, and through the layer, wherein the first mask has a firstoptical density D₁ over the cylindrical volume, wherein the first maskhas a second optical density D₂ over the annular volume, wherein thefirst mask has a third optical density D₃ over the remaining volume, andwherein D₁>D₃>D₂.
 5. The method of claim 4, wherein D₁, D₂, and D₃ havevalues such that the first mask is opaque over the cylindrical volume,transparent over the annular volume, and partially transparent over theremaining volume.
 6. The method of claim 4, wherein the layer in theproviding step includes a power plane between the first surface of thelayer and a second surface of the layer, wherein the power planeincludes a hole therethrough, wherein a perimeter of the hole in thepower plane surrounds the annular volume and a portion of the remainingvolume, and wherein the photolithograhically exposing step furtherincludes forming a second mask over the second surface of the layer andsubsequently passing said radiation through the second mask, onto thesecond surface, and through the layer, wherein the second mask has afourth optical density D₄ over the cylindrical volume, wherein thesecond mask has a fifth optical density D₅ over the annular volume,wherein the second mask has a sixth optical density D₆ over theremaining volume, and wherein D₄>D₆>D₅.
 7. The method of claim 6,wherein D₁, D₂, D₃, D₄, D₅, and D₆ have values such that the first maskand the second mask are each opaque over the cylindrical volume, eachtransparent over the annular volume, and each partially transparent overthe remaining volume.
 8. The method of claim 1, wherein the layer in theproviding step includes a power plane between a first surface of thelayer and a second surface of the layer, wherein the power planeincludes a hole therethrough, wherein a perimeter of the hole in thepower plane circumscribes the annular volume, and wherein thephotolithograhically exposing step includes: forming a first mask overthe first surface of the layer, wherein the first mask is opaque overthe cylindrical volume, transparent over the annular volume, andtransparent over the remaining volume; forming a second mask over thesecond surface of the layer, wherein the second mask is opaque over thecylindrical volume, transparent over the annular volume, and transparentover the remaining volume; passing said radiation through the firstmask, onto the first surface, and through the layer; and passing saidradiation through the second mask, onto the second surface, and throughthe layer.
 9. The method of claim 8, wherein the passing of saidradiation through the first mask and through the layer is for a firstduration, wherein the passing of said radiation through the second maskand through the layer is for a second duration, and wherein the secondduration is about equal to the first duration.
 10. The method of claim1, further comprising developing away the uncured PID material fromwithin the cylindrical volume.
 11. The method of claim 1, wherein theradiation includes ultraviolet radiation.
 12. A method for forming anelectronic structure having a through hole, comprising the steps of:forming a layer that includes a via and an internal power plane having ahole therethrough, wherein a fully cured volume of a photoimageabledielectric (PID) material circumscribes the via, wherein a partiallycured remaining volume of the PID material circumscribes the fully curedvolume, and wherein a perimeter of the hole in the power plane surroundsthe fully cured volume and circumscribes a portion of the remainingvolume; forming a first dielectric layer having a first via, wherein across-sectional area and shape of the first via is about the same as across-sectional area and shape of the via; forming a second dielectriclayer having a second via, wherein a cross-sectional area and shape ofthe second via is about the same as the cross-sectional area and shapeof the via; forming a layered stack, wherein the layer is nonadhesivelysandwiched between the first dielectric layer and the second dielectriclayer, and wherein the via is registered between the first via and thesecond via; and fully curing the remaining volume, wherein the PIDmaterial of the partially cured volume is prevented by the fully curedvolume from entering the via, wherein the layer becomes adhesivelysandwiched between the first dielectric layer and the second dielectriclayer, and wherein the electronic structure is formed such that thethrough hole comprises the first via, the via, and the second via. 13.The method of claim 12, wherein the first dielectric layer includes afirst fully cured PID material, and wherein the second dielectric layerincludes a second fully cured PID material.
 14. The method of claim 12,wherein the first dielectric layer is a first 2S/1P layer, and whereinthe second dielectric layer is a second 2S/1P layer.
 15. The method ofclaim 14, further comprising: forming a first layer on the firstdielectric layer, wherein the first layer includes: a third via having across-sectional area and shape that is about the same as thecross-sectional area and shape of the first via, a first fully curedvolume of a first PID material circumscribing the third via, and a firstpartially cured remaining volume of the first PID materialcircumscribing the first fully cured volume; and forming a second layeron the second dielectric layer, wherein the second layer includes: afourth via having a cross-sectional area and shape that is about thesame as the cross-sectional area and shape of the second via, a secondfully cured volume of a second PID material circumscribing the fourthvia, and a second partially cured remaining volume of the second PIDmaterial circumscribing the second fully cured volume; during the stepof forming a layered stack, nonadhesively layering the first layer onthe first dielectric layer such that the third via is registered overthe first via, and nonadhesively layering the second layer on the seconddielectric layer such that the fourth via is registered over the secondvia; during the fully curing step, adhesively coupling the first layerto the first dielectric layer wherein the PID material of the firstpartially cured volume is prevented by the first fully cured volume fromentering the third via, adhesively coupling the second layer to thesecond dielectric layer wherein the PID material of the second partiallycured volume is prevented by the second fully cured volume from enteringthe fourth via, said fully curing step resulting in the through holefurther comprising the third via and the fourth via.
 16. A layer,comprising: a cylindrical volume; a fully cured annular volume of aphotoimageable dielectric (PID) material circumscribing the cylindricalvolume; and a partially cured remaining volume of the PID materialcircumscribing the annular volume.
 17. The layer of claim 16, whereinthe cylindrical volume includes the PID material in an uncured state.18. The layer of claim 16, wherein the cylindrical volume includes avia.
 19. The layer of claim 18, further comprising a dielectric layer onthe layer of PID material, wherein the dielectric layer includes a firstvia registered over the via, wherein a cross-sectional area and shape ofthe first via is about equal to a cross-sectional area and shape of thevia.
 20. An electronic structure, comprising: a layer that includes: avia, a fully cured volume of a photoimageable dielectric (PID) materialcircumscribing the via, and a partially cured remaining volume of thePID material circumscribing the fully cured volume; and a power planebetween a first surface of the layer and a second surface of the layer,wherein the power plane includes a hole therethrough, wherein aperimeter of the hole in the power plane surrounds the fully curedvolume and circumscribes a portion of the remaining volume.
 21. Theelectronic structure of claim 20, further comprising: a firstsubstructure formed on the first surface of the layer, wherein the firstsubstructure includes a first dielectric layer having a first viaregistered over the via, wherein a cross-sectional area and shape of thefirst via is about the same as a cross-sectional area and shape of thevia, wherein a first signal plane of the first substructure is on afirst surface of the first dielectric layer, wherein a second signalplane of the first substructure is on a second surface of the firstdielectric layer, wherein the first dielectric layer includes a firstpower plane having a therethrough, and wherein the hole of the firstpower plane surrounds the first via; and a second substructure formed onthe second surface of the layer, wherein the second substructureincludes a second dielectric layer having a second via registered overthe via, wherein a cross-sectional area and shape of the second via isabout the same as a cross-sectional area and shape of the via, wherein afirst signal plane of the second substructure is on a first surface ofthe second dielectric layer, wherein a second signal plane of the secondsubstructure is on a second surface of the second dielectric layer,wherein the second dielectric layer includes a second power plane havinga therethrough, and wherein the hole of the second power plane surroundsthe second via.
 22. The method of claim 21, wherein the first dielectriclayer includes a first fully cured PID material, and wherein the seconddielectric layer includes a second fully cured PID material.
 23. Theelectronic structure of claim 21, further comprising: a first layerhaving a first PID material and formed on the first substructure,wherein the first layer includes: a third via registered over the firstvia wherein a cross-sectional area and shape of the third via is aboutthe same as a cross-sectional area and shape of the first via, a firstfully cured volume circumscribing the third via, and a first partiallycured remaining volume circumscribing the first fully cured volume; anda second layer having a second PID material and formed on the secondsubstructure, wherein the second layer includes: a fourth via registeredover the second via wherein a cross-sectional area and shape of thefourth via is about the same as a cross-sectional area and shape of thesecond via, a second fully cured volume circumscribing the fourth via,and a first partially cured remaining volume circumscribing the secondfully cured volume, and wherein the through further includes the thirdvia and the fourth via.
 24. A method for forming an electronicstructure, comprising the steps of: providing a layer that includes: acylindrical volume of a photoimageable dielectric (PID) material, afirst annular volume of the PID material circumscribing the cylindricalvolume, a second annular volume of the PID material circumscribing thefirst annular volume, a remaining volume of the PID materialcircumscribing the second annular volume, and a power plane between afirst surface of the layer and a second surface of the layer, whereinthe power plane includes a hole therethrough, and wherein a perimeter ofthe hole in the power plane circumscribes the second annular volume;photolithograhically exposing the layer to radiation; partially curingthe first annular volume by said radiation; fully curing the secondannular volume by said radiation; partially curing the remaining volumeby said radiation; and preventing curing of the cylindrical volume. 25.The method of claim 24, wherein the photolithograhically exposing stepincludes: forming a first mask over the first surface of the layer,wherein the first mask is opaque over the cylindrical volume,transparent over the first annular volume, transparent over the secondannular volume, and transparent over the remaining volume; forming asecond mask over the second surface of the layer, wherein the secondmask is opaque over the cylindrical volume, opaque over the firstannular volume, transparent over the second annular volume, andtransparent over the remaining volume; passing said radiation throughthe first mask, onto the first surface, and through the layer; andpassing said radiation through the second mask, onto the second surface,and through the layer.
 26. An electronic structure, comprising: a layerthat includes: a via, a first partially cured volume of a photoimageabledielectric (PID) material circumscribing the via, a fully cured volumeof the PID material circumscribing the first partially cured volume, anda second partially cured remaining volume of the PID materialcircumscribing the fully cured volume; and a power plane between a firstsurface of the layer and a second surface of the layer, wherein thepower plane includes a hole therethrough, wherein a perimeter of thehole in the power plane circumscribes the fully cured volume.